High Voltage Direct Current (HVDC) is increasing in usage due to a number of benefits compared to AC (Alternating Current) for power transmission. In order to connect a HVDC link or an HVDC grid to an AC grid, conversion needs to occur from DC (Direct Current) to AC or AC to DC. This conversion can for example be performed using voltage source converters (VSC).
In the voltage source converters, converter cells are controlled by a main controller to synthesize the conversion. When there are many converter cells, each cell needs to be able to receive a control signal from the main controller, which can get complicated when the number of converter cells is large.
WO 2011/120572 presents a voltage source converter for high voltage DC power transmission and reactive power compensation. A presented voltage source converter includes a pair of serial assemblies arranged adjacent to one another to form a ring. Local data transmission links allow slave converter cells of the serial assemblies to receive data from and transmit data to each other. This provides a back-up communication route in the event of a communication failure between a global control unit and a master converter cell of one of the serial assemblies.
However, if possible, it would be beneficial to improve reliability even further in the way control signals are provided to the converter cells.